Less than year after attack, Kvitova faces Williams at Open

The duo could not be separated as they headed to the changeover at 3-3, but a couple of Muguruza errors handed Kvitova three set points, and she took her chance at the first time of asking.

"(The injury) played a quite significant part, and just being injured and not being able to keep that good form", Cilic said.

Cilic, the 2014 US Open champion who had been sidelined since a Wimbledon runner-up showing by an adductor strain, was eliminated by Argentine 29th seed Diego Schwartzman 4-6, 7-5, 7-5, 6-4.

Ninth seeded Williams, a twice US Open champion and a crowd favourite for nearly two decades, takes on Spanish veteran Carla Suarez Navarro in the final women's match on the main showcourt.

The Spaniard will square off with No.13-seeded Petra Kvitova for a spot in the quarterfinals on Monday. "I'm not sure where she (Wozniacki) is", shot back Sharapova, adding she would be happy to play in parking lot if that is where she was scheduled.

She won Birmingham, and then strung together a few good wins through the hard-court swing towards the US Open, but faced a really tough draw in NY.

Shapovalov will play for a quarter-final berth against Spanish 12th seed Pablo Carreno Busta, who ousted French qualifier Nicolas Mahut 6-3, 6-4, 6-3.

Baby news from Florida turned heads at the year's final Grand Slam event as Williams, a 23-time Grand Slam champion, gave birth to the child she was pregnant with when she won the Australian Open in January. "I didn't come to the US Open to be number one. that wasn't really my goal". It was a vital hold, and she went on to break in the next and level the set at 4-4. She is the only woman in the draw to have reached two Major finals this year, yet this was the No9 seed's 19th appearance at the US Open-and she reached the final on her debut as a teenager in 1997.

Williams is, at 37, the oldest woman who entered the tournament. Only current number one Karolina Pliskova and fourth-seeded Elina Svitolina could deny her reaching the top for the first time.

Kvitova is a two-time Wimbledon champion, but her ability to continue to contend for major titles - or even play at all - had been in doubt after a vicious knife attack during a home invasion in December severely damaged her left hand.

Meanwhile, Sloane Stephens of the United States reached the last eight at the Flushing Meadows for the first time by upsetting Julia Goerges 6-3, 3-6, 6-1.